docs: add block/mute user relations, emoji-sync CLI, and uid indexes

- Add `/block`, `/mute` endpoints with block/unblock and mute/unmute functionality in `routers/relations.py`, hiding blocked users' content everywhere except their own profile while muting only suppresses notifications
- Introduce `devplace emoji-sync` CLI command to regenerate `static/js/emoji-shortcodes.js` from the emoji library, documented in `CLAUDE.md` and wired in `cli.py`
- Create `get_blocked_uids()` database helper and apply it in `content.py` `load_detail()` to filter blocked users' posts from detail views
- Implement `_uid_index()` and `_drop_index()` helpers in `database.py` for unique uid indexes across tables, with `user_relations` added to `SOFT_DELETE_TABLES`
- Document new routes in `AGENTS.md` and `README.md`, including emoji shortcodes rendering behavior distinct from the emoji picker

README.md

@@ -78,6 +78,8 @@ devplacepy/
 | `/bookmarks` | Save/unsave content; `/bookmarks/saved` personal list |
 | `/polls` | Vote on post-attached polls |
 | `/follow` | Follow/unfollow users |
+| `/block` | Block/unblock a user: hides all of their posts, comments and messages from you everywhere except their own profile, and stops them notifying you |
+| `/mute` | Mute/unmute a user: stops them creating notifications for you while their content stays visible |
 | `/leaderboard` | Contributor ranking by total stars earned |
 | `/avatar` | Multiavatar proxy with in-memory cache |
 | `/issues` | Issue tracker backed by Gitea: list/detail/comment/status, AI-enhanced filing, admin planning report of all open tickets |
@@ -111,6 +113,7 @@ Every AI gateway response (`/openai/v1/*`) also returns per-call `X-Gateway-*` h
 ## Engagement
 
 - **Emoji reactions** - a fixed palette of reactions on posts, comments, gists, and projects, separate from voting and carrying no ranking weight.
+- **Emoji shortcodes** - typing a `:name:` shortcode in any content (posts, comments, titles, project and gist descriptions, news, and direct messages) renders the matching emoji, using the full GitHub/Discord standard set (for example `:rocket:` becomes a rocket). Server-rendered and live content share one shortcode list; unknown names and shortcodes inside code are left untouched. Documented at `/docs/emoji-shortcodes`. This is distinct from the visual emoji-picker button in the composer, which inserts the literal emoji character.
 - **Polls** - a post can carry a poll (question plus up to six options); results appear as live bars once the viewer votes, one vote per member. A poll can be attached when the post is created or added later by editing a post that has none.
 - **Bookmarks** - save posts, gists, projects, and news to a personal list at `/bookmarks/saved`.
 - **Private projects** - an owner can mark a project private so it is visible only to them (and administrators) and excluded from listings, profiles, search, the sitemap, and zip access. Set at creation or toggled later from the project page.